From Netherlands patent publication No. 6716106, it is known that molding compositions based on one or more of the thermoplastic polyphenylene ethers and one or more of the thermoplastic polysulfones, when molded at elevated temperature and pressure, provide shaped articles which possess very satisfactory impact strength. However, samples molded from such compositions show phase incompatibility in differential scanning calorimetry tests and the moldings are laminar. It is obvious if this shortcoming is avoided, then the compositions will provide molded articles which are superior in the above respects. It has now been discovered that the impact properties and heat age resistance is increased, and lamination is decreased or even eliminated, when the molding composition has a content of a selectively hydrogenated linear or radial thermoplastic block copolymer which consists essentially of vinyl aromatic compound, e.g., styrene and a diene, e.g. butadiene.
It has further been found that properties, especially impact strength and processability can be further improved by adding an effective amount of a plasticizer, e.g. triphenyl phosphate. The preferred plasticizers also function to enhance the flame retardancy of the new compositions.
Suitable block copolymers are commercially available at low cost. The present invention thus substantially expands the field of utility of polyphenylene ether--polysulfone moldings in an economical way.